Since the impinging signal sources in most RF environments are distributed over a very wide physical area, an RF survey concerned with signal sources within a limited physical region is difficult due to the effort of manually determining which signals are in the region of interest.
Known patent documents include:
U.S. Pat. No. 4,353,073;
U.S. Pat. No. 4,903,333;
U.S. Pat. No. 6,218,987;
U.S. Pat. No. 6,664,921; and
U.S. Pat. No. 6,680,709.